The present invention generally relates to devices for injecting liquid medications from prefilled cartridges and more particularly to single use disposable syringe assemblies for injecting local anesthetics.
Many dental procedures use anesthetic to numb an area of a patient's mouth to reduce pain and discomfort a patient may feel. Conventionally, a re-usable breech-loading, metallic, cartridge-type syringe assembly is used to inject the anesthetic. The dental syringe assembly includes a syringe, a cartridge, and a needle. The syringe may be constructed of chrome-plated brass and stainless steel and may include a needle adapter, a syringe barrel, a plunger rod, a finger grip, and a thumb ring. Typically, the syringe must be sterilized before each use.
Generally, the cartridge or carpule is a vial containing a local anesthetic among other ingredients. The cartridge may include a glass cylinder, a piston, and a rubber diaphragm held in position by an aluminum band. The cartridge is usually wiped with alcohol prior to being loaded into the syringe.
The needle of the dental syringe permits local anesthetic to travel from the dental cartridge into tissue surrounding the needle tip. Needles may be pre-sterilized and disposable. The needle may consist of a single piece of metal tubing surrounded by a plastic or a metal needle hub attached to the needle adapter of the syringe.
Assembly of a dental syringe often requires removing a sterilized syringe from its container and placing an alcohol wiped cartridge into the syringe with the plunger rod of the syringe fully retracted. The rubber diaphragm on a distal end of the cartridge is inserted into the syringe first and the plunger rod engages the piston positioned at a proximal end of the cartridge. The syringe includes an access needle for puncturing the cartridge. As the plunger rod advances, anesthetic is forced out of the cartridge toward a need assembly. The needle assembly including a needle and protective cap may be secured to the syringe. The protective cap is removed from the needle and the syringe is ready for use.
After the assembled dental syringe is used, the needle assembly must be recapped, disconnected from the syringe and disposed in a sharps container, and the cartridge must be removed and disposed in a biohazard bag or sharps container. Thereafter, the syringe may be sterilized for its next use.